So he's a director and an employee? Different considerations apply for each position. If he's a director, then the rules about removing directors will be in your Articles of Association - sometimes it can just be by board resolution, but you may have to go to the shareholders.
As an employee, if he has been working for you for longer than a year, then the Unfair Dismissals Act applies and the company could be liable if you don't follow the right procedures. It sounds like a redundancy situation to me if you are closing the entire section but you'll have to get proper advice on that front and follow the rules in the UDA for cases of redundancy. A genuine redundancy shouldn't cost the company that much.
At the moment, he's both a director and an employee - removing him as a director doesn't make him "revert" to anything. Someone can be a director or an employee or both at the same time. You don't lose employment rights if you are also a director.
If someone is a director and employee, you should have a clause in their contract of directorship/employment saying that he'll resign from the board if his employment is terminated for any reason (late advice probably, but bear in mind for next time)
Sprite